JP5192638B2 - Ink composition, image forming method using the same, and recorded matter - Google Patents

Description

  The present invention relates to an ink composition, an image forming method using the same, and a recorded matter obtained thereby. Furthermore, the present invention is suitably used for image recording, is cured by irradiation with active energy rays, has a small curl after curing, and has a low odor, an image forming method using the same, and an image composition obtained thereby. Related to recorded material.

  Water-based ink-jet ink has poor water resistance and tends to cause bleeding when printed on plain paper. In addition, when printing is performed on a non-water-absorbing recording medium such as plastic, adhesion of ink droplets is poor. For this reason, image formation cannot be performed, and the image tends to blur. Furthermore, since the drying of the solvent is extremely slow, it is necessary to dry the printed matter without overlapping immediately after printing.

  As an improvement, an ultraviolet curable ink using a polyfunctional monomer suitable for printing on a non-water-absorbing recording medium and having excellent adhesion to the recording medium has been developed. However, this was slow to dry due to the water-dispersed ink and was insufficient to form a full-color image. In order to solve the drying property, a method using a volatile organic solvent as an ink solvent has been performed, but a method using no highly volatile solvent has been desired.

In order to solve these problems, ink-jet inks that are cured and fixed by active energy rays rather than volatilization of the ink solvent have been developed. For example, Patent Documents 1 to 3 disclose inks containing a monomer having a polymerizable group and an oil-soluble dye. However, these compounds contain a large amount of low molecular weight compounds as polymerizable compounds, and unreacted polymerizable compounds remain. In addition, curling occurs in the printed matter due to volume shrinkage due to polymerization.
On the other hand, an ink containing a specific polymerizable compound and a polymerizable compound having a molecular weight of 400 or more has been disclosed for the purpose of enhancing skin irritation and adhesion. However, this also contains a lot of low boiling points, and curls are generated because the molecular weight is insufficient.
JP 2003-221528 A JP 2003-221532 A JP 2003-221530 A JP 2003-192943 A

  An object of the present invention is to provide an ink composition which is excellent in ink stability and light resistance and has a low odor. Another object of the present invention is to provide an ink composition that reduces curling of the recording material after curing due to volume shrinkage, an image forming method using the ink composition, and a recorded matter obtained thereby.

The above problems have been solved by the following means.
(1) An ink composition containing a) a photopolymerization initiator and b) a polymerizable compound, wherein the content of the polymerizable compound of b) is 70 to 99.9 mass with respect to the total mass of the ink composition. The tridecyl acrylate, the methoxy polyethylene glycol monoacrylate, the polyethylene glycol diester having a molecular weight per polymerizable functional group of 250 to 2000 is 50% by mass or more of the total mass of the polymerizable compound of the above b). acrylate, and at least one polymerizable compound der selected from the group consisting of polypropylene glycol diacrylate is, the molecular weight of the content of organic compounds of less than 250, relative to the total weight of the composition, less than 10 wt% jet printing ink composition characterized der Rukoto.
(2) From b) 75% by mass or more of the total mass of the polymerizable compound having a molecular weight of 300 or more per polymerizable functional group, from tridecyl acrylate, methoxypolyethylene glycol monoacrylate, polyethylene glycol diacrylate, and polypropylene glycol diacrylate The ink composition for ink jet printing according to (1), wherein the ink composition is at least one polymerizable compound selected from the group consisting of:
( 3 ) The ink composition for ink jet printing according to (1) or (2) , comprising a colorant.
( 4 ) The ink composition for inkjet printing according to ( 3 ), wherein the colorant is selected from the group consisting of a pigment and an oil-soluble dye.
( 5 ) The ink composition for inkjet printing according to ( 4 ), wherein an oxidation potential of the oil-soluble dye is at least 1.0 V (vs SCE).
( 6 ) Image formation comprising an image recording step of recording an image on a recording medium by inkjet recording that discharges the ink composition for inkjet printing according to any one of (1) to ( 5 ) Method.
( 7 ) An image recording step of recording an image on a recording medium using the ink composition for ink jet printing according to any one of (1) to ( 5 ),
An image curing step of irradiating and curing an active energy ray on the image recorded on the recording medium in the image recording step;
An image forming method comprising:
( 8 ) The image forming method according to ( 7 ), wherein the image recording step records the image by inkjet recording in which the ink composition for inkjet printing is ejected.
( 9 ) A recorded matter recorded using the ink composition for ink jet printing according to any one of (1) to ( 5 ).

    The ink composition of the present invention can be cured rapidly, has high stability and high light resistance, can be used as an excellent image forming method, and a recorded matter obtained by the method, and can be obtained even in the presence of a colorant. The effect is remarkable. The ink composition of the present invention can reduce the odor after printing by using a large amount of a low odor and high molecular weight polymerizable compound. Furthermore, the ratio of the polymerizable functional group that is the volume shrinkage portion can be reduced, the curling of the recording body after curing can be reduced, and an excellent image forming method and a recorded matter obtained thereby can be obtained. .

Hereinafter, the ink composition for ink jet printing of the present invention (hereinafter simply referred to as an ink composition) will be described in detail.
The b) polymerizable compound used in the present invention is a compound that cures by causing a polymerization reaction by applying some energy, and can be used regardless of the type of monomer, oligomer, or polymer. A compound having a functional functional group is preferred. b) The polymerizable compound is at least one polymerizable compound selected from the group consisting of tridecyl acrylate, methoxypolyethylene glycol monoacrylate, polyethylene glycol diacrylate, and polypropylene glycol diacrylate, which satisfies the molecular weight condition. The content in the ink composition is in the range of 70% to 99.9% by mass, preferably 75% to 99% by mass, and preferably 80% to 97% by mass with respect to the total mass of the ink composition. % Is more preferable. By setting it within this range, a) the amount of the photopolymerization initiator and the colorant is well balanced, and sufficient curing performance can be obtained.

  The inkjet ink that is cured by the active energy ray includes b) a polymerizable compound. Generally, it contains volatile substances and has an odor. From the viewpoint of suppressing volatility, the molecular weight is preferably large, and it is preferable that the polymerizable compound b) having a molecular weight of 300 or more in the ink composition of the present invention is included. Furthermore, from the viewpoint of reducing this odor, the polymerizable compound having a molecular weight of 300 or more (more preferably 300 to 2000) is 70% by mass or more and 100% by mass or less with respect to the total mass of the polymerizable compound b). Is more preferably 75% by mass or more and 100% by mass or less, and particularly preferably 80% by mass or more and 95% by mass or less.

When the ink composition is irradiated with active energy rays, a polymerization initiating species is generated by the photopolymerization initiator in the ink, and the polymerizable compound is polymerized to form a thin film. Generally, shrinkage occurs at this curing stage, and curling and adhesion are reduced. As a means for preventing this, it is effective to reduce the ratio of polymerizable functional groups that cause volume shrinkage. In the ink composition of the present invention, the molecular weight of the polymerizable compound is divided by the number of polymerizable functional groups. The value (molecular weight per polymerizable functional group) is 250 or more. In terms of volume shrinkage suppression, the molecular weight per polymerizable functional group may a larger, but as the upper limit in the too large viscosity increases, a 2000, more preferably 1000, particularly in the preferred 750 is there. The content of the polymerizable compound having a molecular weight of 250 or more per polymerizable functional group is preferably 50% by mass or more and 99% by mass or less, and 60% by mass or more and 95% by mass or less, based on the total mass of the polymerizable compound. Is more preferable, and 75 mass% or more and 95 mass% or less are especially preferable.
In the ink composition of the present invention, the polymerizable compounds may be used alone or in combination of two or more, as long as the effects of the present invention are not hindered.

  As described above, when the molecular weight or content of the polymerizable compound is not preferable, odor is generated, and curling and adhesion are reduced. This is not limited to the polymerizable compound. In the ink composition of the present invention, particularly from the viewpoint of odor, the content of the compound having a molecular weight of less than 250 (preferably 15 to 200) is based on the total mass of the ink composition. Less than 10% by mass, preferably 0 to 8% by mass, and more preferably 0 to 5% by mass.

  In the ink composition of the present invention, various monomers can be used in combination as the polymerizable compound as long as the effects of the present invention are not hindered. For example, vinyl compounds such as (meth) acrylates, (meth) acrylamides, styrene derivatives, vinyl ethers, 1,3-dienes, ring-opening polymerizable compounds such as oxirane compounds, oxetane compounds, tetrahydrofuran, lactams, and lactones are used. Of these, (meth) acrylate, vinyl ether, styrene derivatives, oxirane compounds, and oxetane compounds are preferably used.

[Photopolymerization initiator]
The a) photopolymerization initiator used in the ink composition of the present invention is not limited in its structure, and any one selected from a photoradical polymerization initiator and a photocationic polymerization initiator can be used.
However, from the viewpoint of decomposing the thermal polymerization initiator, when using a radical photopolymerization initiator, the polymerizable functional group is acryloyl group, methacryloyl group, α-substituted acryloyl group, acrylamide group, methacrylamide group, styryl group, vinyl ether. A polymerizable compound having a radical polymerizable functional group such as a group or an allyl group must be contained. Of these, radical polymerizable compounds having an acryloyl group, a methacryloyl group, an α-substituted acryloyl group, an acrylamide group, and a methacrylamide group are preferably used from the viewpoint of polymerization rate. When a photocationic polymerization initiator is used, a cationic functional vinyl monomer such as a styryl group, an α-methylstyryl group, a vinyl ether group, an isopropyl ether group, an α-substituted vinyl ether group, a cyclic ether, It is necessary to contain a cationically polymerizable compound such as cyclic carbonate, lactam, and lactone, and from the viewpoint of polymerization rate, a cationically polymerizable vinyl monomer such as a styryl group, an α-methylstyryl group, a vinyl ether group, or an isopropyl ether group should be used. preferable.

In the ink composition of the present invention, the photo cationic polymerization initiator refers to a compound that generates an acid upon irradiation with an active energy ray to initiate cationic polymerization, and appropriately selects commonly used compounds and mixtures thereof. Can be used.
A photocationic polymerization initiator can be used individually or in combination of 2 or more types.
Examples of the photocationic polymerization initiator in the present invention include diazonium salts, phosphonium salts, sulfonium salts, iodonium salts, imide sulfonates, oxime sulfonates, diazodisulfones, disulfones, and o-nitrobenzyl sulfonates.
Further, these photocationic polymerization initiators, or compounds obtained by introducing a group or compound having an equivalent function into the main chain or side chain of the polymer, for example, US Pat. No. 3,849,137, German Patent No. 3914407. JP, 63-26653, JP 55-164824, JP 62-69263, JP 63-146038, JP 63-163452, JP 62-153853, The compounds described in JP-A-63-146029 can be used.
Furthermore, compounds capable of generating an acid by light described in US Pat. No. 3,779,778, European Patent 126,712 and the like can also be used.

  Preferred examples of the photoacid generator used in the ink composition of the present invention include compounds represented by the following general formulas (b1), (b2), and (b3).

In general formula (b1), R ²⁰¹ , R ²⁰² and R ²⁰³ each independently represents an organic group.
X ⁻ represents a non-nucleophilic anion, preferably a sulfonate anion, a carboxylate anion, a bis (alkylsulfonyl) amide anion, a tris (alkylsulfonyl) methide anion, BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ or the following The organic anion which has a carbon atom is preferable.

  Preferable organic anions include organic anions represented by the following formula.

Rc ¹ represents an organic group.
Examples of the organic group in Rc ¹ include those having 1 to 30 carbon atoms, and preferably an alkyl group, a cycloalkyl group, an aryl group, or a plurality of these are a single bond, —O—, —CO ₂ —, —S. _{-, - SO 3 -, -} SO 2 N (Rd 1) - can be exemplified linked group a linking group such as.

Rd ¹ represents a hydrogen atom or an alkyl group. Rc ³ , Rc ⁴ and Rc ⁵ each independently represents an organic group. Preferred examples of the organic group for Rc ³ , Rc ⁴ , and Rc ⁵ include the same organic groups as those for Rc ¹ , and most preferred is a perfluoroalkyl group having 1 to 4 carbon atoms. Rc ³ and Rc ⁴ may be bonded to form a ring. Examples of the group formed by combining Rc ³ and Rc ⁴ include an alkylene group and an arylene group. A perfluoroalkylene group having 2 to 4 carbon atoms is preferred.

The organic group of Rc ¹ and Rc ³ -Rc ⁵ is particularly preferably an alkyl group substituted at the 1-position with a fluorine atom or a fluoroalkyl group, or a phenyl group substituted with a fluorine atom or a fluoroalkyl group. By having a fluorine atom or a fluoroalkyl group, the acidity of the acid generated by light irradiation is increased and the sensitivity is improved.

The organic groups as R ²⁰¹ , R ²⁰² and R ²⁰³ are generally organic groups having 1 to 30 carbon atoms, preferably 1 to 20 organic groups.
Two of R ^{201 to} R ²⁰³ may be bonded to form a ring structure, and the ring may contain an oxygen atom, a sulfur atom, an ester bond, an amide bond, or a carbonyl group. Examples of the group formed by combining two of R ^{201 to} R ²⁰³ include an alkylene group (eg, butylene group, pentylene group).

Specific examples of the organic group as R ²⁰¹ , R ²⁰² and R ²⁰³ include corresponding groups in the compounds (b1-1), (b1-2) and (b1-3) described later.
In addition, the compound which has two or more structures represented by general formula (b1) may be sufficient. For example, at least one of ^R 201 ^{to R 203} of the compound represented by the general formula (b1) is at least one directly with ^R 201 ^{to R 203} of another compound represented by formula (b1), or, It may be a compound having a structure bonded through a linking group.

Further preferred examples of the component (b1) include compounds (b1-1), (b1-2), and (b1-3) described below.
Compound (b1-1) is in which at least one aryl group ^R 201 ^{to R 203} in formula (b1), arylsulfonium compound, i.e., a compound having arylsulfonium as a cation.
In the arylsulfonium compound, all of R ^{201 to} R ²⁰³ may be an aryl group, or a part of R ^{201 to} R ²⁰³ may be an aryl group, and the rest may be an alkyl group or a cycloalkyl group.
Examples of the arylsulfonium compound include triarylsulfonium compounds, diarylalkylsulfonium compounds, aryldialkylsulfonium compounds, diarylcycloalkylsulfonium compounds, aryldicycloalkylsulfonium compounds, and the like.
The aryl group of the arylsulfonium compound is preferably an aryl group such as a phenyl group or a naphthyl group, or a heteroaryl group such as an indole residue or a pyrrole residue, more preferably a phenyl group or an indole residue. When the arylsulfonium compound has two or more aryl groups, the two or more aryl groups may be the same or different.

As the alkyl group that the arylsulfonium compound has as necessary, a linear or branched alkyl group having 1 to 15 carbon atoms is preferable, for example, a methyl group, an ethyl group, a propyl group, an n-butyl group, A sec-butyl group, a t-butyl group, etc. can be mentioned.
The cycloalkyl group that the arylsulfonium compound has as necessary is preferably a cycloalkyl group having 3 to 15 carbon atoms, and examples thereof include a cyclopropyl group, a cyclobutyl group, and a cyclohexyl group.
The aryl group, alkyl group, and cycloalkyl group of R ^{201 to} R ²⁰³ are an alkyl group (for example, 1 to 15 carbon atoms), a cycloalkyl group (for example, 3 to 15 carbon atoms), an aryl group (for example, 6 carbon atoms). -14), an alkoxy group (for example, having 1 to 15 carbon atoms), a halogen atom, a hydroxyl group, or a phenylthio group may be substituted. Preferred substituents are linear or branched alkyl groups having 1 to 12 carbon atoms, cycloalkyl groups having 3 to 12 carbon atoms, and linear, branched or cyclic alkoxy groups having 1 to 12 carbon atoms. And most preferably an alkyl group having 1 to 4 carbon atoms and an alkoxy group having 1 to 4 carbon atoms. The substituent may be substituted with any one of three R ^{201 to} R ²⁰³ , or may be substituted with all three. Further, when R ^{201 to} R ²⁰³ are an aryl group, the substituent is preferably substituted at the para position of the aryl group.

Next, the compound (b1-2) will be described.
The compound (b1-2) is a compound when R ^{201 to} R ²⁰³ in the formula (b1) each independently represents an organic group that does not contain an aromatic ring. Here, the aromatic ring includes an aromatic ring containing a hetero atom.
The organic group not containing an aromatic ring as R ^{201 to} R ²⁰³ generally has 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms.
R ^{201 to} R ²⁰³ are each independently preferably an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group, more preferably a linear, branched, cyclic 2-oxoalkyl group, or an alkoxycarbonylmethyl group, particularly preferably Is a linear, branched 2-oxoalkyl group.
The alkyl group as R ^{201 to} R ²⁰³ may be either linear or branched, and is preferably a linear or branched alkyl group having 1 to 10 carbon atoms (for example, a methyl group, an ethyl group, Propyl group, butyl group, pentyl group), and a straight chain, branched 2-oxoalkyl group, and alkoxycarbonylmethyl group are more preferable.
The cycloalkyl group as R ^{201 to} R ²⁰³ is preferably a cycloalkyl group having 3 to 10 carbon atoms (cyclopentyl group, cyclohexyl group, norbornyl group), and more preferably a cyclic 2-oxoalkyl group. .
Preferred examples of the linear, branched and cyclic 2-oxoalkyl group represented by R ^{201 to} R ²⁰³ include a group having> C═O at the 2-position of the above alkyl group or cycloalkyl group.
The alkoxy group in the alkoxycarbonylmethyl group as R ^{201 to} R ²⁰³ is preferably an alkoxy group having 1 to 5 carbon atoms (methoxy group, ethoxy group, propoxy group, butoxy group, pentoxy group).
R ^{201 to} R ²⁰³ may be further substituted with a halogen atom, an alkoxy group (for example, having 1 to 5 carbon atoms), a hydroxyl group, a cyano group, or a nitro group.

  The compound (b1-3) is a compound represented by the following general formula (b1-3), and is a compound having a phenacylsulfonium salt structure.

In General Formula (b1-3), R ^{1c to} R ^5c each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an alkoxy group, or a halogen atom.
R ^6c and R ^7c each independently represents a hydrogen atom, an alkyl group or a cycloalkyl group.
R ^x and R ^y each independently represents an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group.
Any two or more of R ^{1c to} R ^5c , R ^6c and R ^7c , and R ^x and R ^y may be bonded to each other to form a ring structure.
Zc ^- represents a non-nucleophilic anion, in the general formula (b1) X ^- can be the same as the non-nucleophilic anion.

The alkyl group as R ^{1c to} R ^7c may be either linear or branched, for example, a linear or branched alkyl group having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms. (For example, a methyl group, an ethyl group, a linear or branched propyl group, a linear or branched butyl group, a linear or branched pentyl group).
Preferred examples of the cycloalkyl group represented by R ^{1c to} R ^7c include cycloalkyl groups having 3 to 8 carbon atoms (for example, a cyclopentyl group and a cyclohexyl group).
The alkoxy group as R ^{1c to} R ^{5c may} be linear, branched or cyclic, for example, an alkoxy group having 1 to 10 carbon atoms, preferably a linear or branched chain having 1 to 5 carbon atoms. An alkoxy group (for example, a methoxy group, an ethoxy group, a linear or branched propoxy group, a linear or branched butoxy group, a linear or branched pentoxy group), a cyclic alkoxy group having 3 to 8 carbon atoms (for example, a cyclopentyloxy group, Cyclohexyloxy group).
Examples of the group formed by combining any two or more of R ^{1c to} R ^5c , R ^6c and R ^7c , and R ^x and R ^y include a butylene group and a pentylene group. This ring structure may contain an oxygen atom, a sulfur atom, an ester bond, or an amide bond.

Preferably any one of R ^{1c to} R ^5c is a linear or branched alkyl group, a cycloalkyl group, or a linear, branched or cyclic alkoxy group, and more preferably the sum of the carbon atoms of R ^1c to R ^5c Is 2-15. Thereby, solvent solubility improves more and generation | occurrence | production of a particle is suppressed at the time of a preservation | save.
^Examples of the alkyl group and cycloalkyl group as R ^x and R ^y include the same alkyl groups and cycloalkyl groups as R ^{1c to} R ^7c .
R ^x and R ^y are preferably a 2-oxoalkyl group or an alkoxycarbonylmethyl group.
Examples of the 2-oxoalkyl group include a group having> C═O at the 2-position of the alkyl group or cycloalkyl group as R ^{1c to} R ^5c .
The alkoxy group in the alkoxycarbonylmethyl group may be the same as the alkoxy group as R ^1c to R ^5c.
R ^x and R ^y are preferably an alkyl group or cycloalkyl group having 4 or more carbon atoms, more preferably 6 or more, and still more preferably 8 or more alkyl groups or cycloalkyl groups.

In the formula ^{(b2), (b3),} R 204 ~R 207 each independently represents an aryl group, an alkyl group or a cycloalkyl group. X ⁻ represents a non-nucleophilic anion, and examples thereof include the same non-nucleophilic anion as X ^{− in} formula (b1).
The aryl group for R ^{204 to} R ²⁰⁷ is preferably a phenyl group or a naphthyl group, and more preferably a phenyl group.
The alkyl group as R ^{204 to} R ²⁰⁷ may be either linear or branched, and is preferably a linear or branched alkyl group having 1 to 10 carbon atoms (for example, a methyl group, an ethyl group, Propyl group, butyl group, pentyl group). Preferable examples of the cycloalkyl group as R ^{204 to} R ²⁰⁷ include a cycloalkyl group having 3 to 10 carbon atoms (cyclopentyl group, cyclohexyl group, norbornyl group).
Examples of the substituent that R ^{204 to} R ²⁰⁷ may have include an alkyl group (for example, 1 to 15 carbon atoms), a cycloalkyl group (for example, 3 to 15 carbon atoms), and an aryl group (for example, carbon atoms). (Chemical formula 6-15), an alkoxy group (for example, C1-C15), a halogen atom, a hydroxyl group, a phenylthio group etc. can be mentioned.

  Examples of the photocationic polymerization initiator further include compounds represented by the following general formulas (b4), (b5), and (b6).

In general formulas (b4) to (b6), Ar ³ and Ar ⁴ each independently represents an aryl group.
R ²⁰⁶ , R ²⁰⁷ and R ²⁰⁸ each independently represents an alkyl group, a cycloalkyl group or an aryl group. A represents an alkylene group, an alkenylene group or an arylene group.

Preferable examples of the cationic photopolymerization initiator include compounds represented by general formulas (b1) to (b3).
Specific examples of the preferred cationic photopolymerization initiator used in the ink composition of the present invention are illustrated below, but the present invention is not limited thereto.

Further, oxazole derivatives and s-triazine derivatives described in JP-A No. 2002-122994, paragraph numbers [0029] to [0030] are also preferably used.
The onium salt compounds and sulfonate compounds exemplified in JP-A-2002-122994, paragraphs [0037] to [0063] can also be suitably used in the present invention.

The radical photopolymerization initiator used in the present invention refers to a compound that generates active radical species by applying active light and initiates and accelerates the polymerization reaction of the ink composition. Can be used.
Examples of the photo radical polymerization initiator include acetophenone compounds, benzoin compounds, benzophenone compounds, thioxanthone compounds, benzyl compounds, acylphosphine oxide compounds, and the like. Examples of the acetophenone compound include 2,2-diethoxyacetophenone, 2-hydroxymethyl-1-phenylpropan-1-one, 4′-isopropyl-2-hydroxy-2-methyl-propiophenone, 2-hydroxy -2-methyl-propiophenone, p-dimethylaminoacetone, p-tert-butyldichloroacetophenone, p-tert-butyltrichloroacetophenone, p-azidobenzalacetophenone, 1-hydroxycyclohexyl phenyl ketone and the like. Examples of the benzoin compounds include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin-n-propyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, and benzyldimethyl ketal. Examples of the benzophenone compounds include benzophenone, methyl o-benzoylbenzoate, Michler's ketone, 4,4′-bisdiethylaminobenzophenone, 4,4′-dichlorobenzophenone, and the like. Examples of the thioxanthone compound include thioxanthone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, and the like. Examples of the benzyl compound include benzyl and benzyl-β-methoxyethyl acetal. Examples of the acyl phosphine oxide compound include bis (2,6-dimethoxybenzoyl) (2,4,4-trimethylpentyl) phosphine oxide, 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, and the like.
There is no restriction | limiting in particular in content of a photoinitiator in the ink composition of this invention, 0.1-20 mass% is contained with respect to the total mass of a composition in the range which does not prevent the effect of this invention. It is preferable and 0.5-15 mass% is more preferable.

[Active energy rays]
Examples of active energy rays for proceeding the polymerization of the ink composition of the present invention include ultraviolet rays, far ultraviolet rays, visible rays, g rays, h rays, i rays, KrF excimer laser light, ArF excimer laser light, and electron beams. X-rays, molecular beams, ion beams, α-rays, γ-rays, and the like, and α-rays, γ-rays, X-rays, ultraviolet rays, visible rays, electron beams, and the like can be preferably used. Of these, ultraviolet rays and visible rays are preferably used from the viewpoint of cost and safety, and ultraviolet rays are more preferably used.
As a light source for generating ultraviolet rays, low-pressure mercury lamps, high-pressure mercury lamps, short arc discharge lamps, ultraviolet light-emitting diodes, and the like can be used, and high-pressure mercury lamps belonging to high-pressure discharge lamps with light amounts and wavelengths suitable for initiators. Xenon lamps belonging to metal halide lamps and short arc discharge lamps are preferably used. Moreover, an ultraviolet light emitting diode is also preferably used from the viewpoint of energy saving.

[Polymerization inhibitor]
In the ink composition of the present invention, it is preferable to use in combination with a polymerization inhibitor that inhibits the progress of polymerization other than cationic polymerization in order to effectively proceed the polymerization with the photocationic polymerization initiator.
Suitable polymerization inhibitors include phenolic hydroxyl group-containing compounds and quinones, N-oxide compounds, piperidine 1-oxyl free radical compounds, pyrrolidine 1-oxyl free radical compounds, N-nitrosophenylhydroxylamines, and cations It is a compound selected from the group consisting of dyes. Preferred polymerization inhibitors include haloquinone, p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, resorcinol, catechol, t-butylcatechol, hydroquinone, benzoquinone, 4,4-thiobis (3-methyl-6- t-butylphenol), 2,2′-methylenebis (4-methyl-6-t-butylphenol), 2,2,6,6-tetramethylpiperidine and its derivatives, di-t-butylnitroxide, 2,2,6 , 6-tetramethylpiperidine-N-oxide and its derivatives, such as piperidine 1-oxyl free radical, 2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-oxo-2,2,6,6 -Tetramethylpiperidine 1-oxyl free radical, 4-hydroxy-2,2,6,6-tetramethylpiperidine -Oxyl free radical, 4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-maleimido-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-phosphonoxy -2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 3-carboxy-2,2,5,5-tetramethylpyrrolidine 1-oxyl free radical, N-nitrosophenylhydroxylamine cerium salt, Examples thereof include N-nitrosophenylhydroxylamine aluminum salt, crystal violet, methyl violet, ethyl violet and Victoria pure blue BOH. In the ink composition of the present invention, the addition amount of the polymerization inhibitor is not particularly limited, and 0.0001 to 1% by mass with respect to the total mass of the composition may be added within a range not impeding the effects of the present invention. preferable.

[Colorant]
The ink composition of the present invention does not require a colorant in the case of a colorless ink composition, but a colorant can be preferably added to form a visible image. In the present invention, a colorant is contained. Even in the ink composition, the effect is effectively exhibited.
There is no restriction | limiting in particular in the coloring agent which can be used here, According to a use, various color materials and (pigment, dye) can be selected suitably and can be used. For example, when forming an image excellent in weather resistance, a pigment is preferable. As the dye, both water-soluble dyes and oil-soluble dyes can be used as long as they are soluble in the polymerizable compound. In the present invention, in order to form an image or characters, the ink composition of the present invention preferably contains a pigment or an oil-soluble dye as a colorant.
The addition amount of these colorants is preferably 0.5 to 20% by mass, more preferably 1 to 15% by mass, with respect to the total mass of the composition, as long as the effects of the present invention are not hindered. 5 to 15% by mass is particularly preferable.

[Pigment]
The pigments preferably used in the ink composition of the present invention will be described.
The pigment is not particularly limited, and all commercially available organic and inorganic pigments or pigments dispersed in an insoluble resin or the like as a dispersion medium, or the resin is grafted onto the pigment surface Can be used. Moreover, what dye | stained the resin particle with dye can be used.
Examples of these pigments include, for example, “Spirit of Pigments” edited by Seijiro Ito (2000), W. Herbst, K. Hunger, “Industrial Organic Pigments”, JP 2002-12607 A, JP 2002-188025 A. Examples thereof include pigments described in JP-A No. 2003-26978 and JP-A No. 2003-342503.

  Specific examples of organic pigments and inorganic pigments that can be used in the present invention include C.I. I. Pigment Yellow 1 (Fast Yellow G etc.), C.I. I. A monoazo pigment such as C.I. Pigment Yellow 74; I. Pigment Yellow 12 (disaji yellow AAA, etc.), C.I. I. Disazo pigments such as C.I. Pigment Yellow 17; I. Non-benzidine type azo pigments such as CI Pigment Yellow 180; I. Azo lake pigments such as C.I. Pigment Yellow 100 (eg Tartrazine Yellow Lake); I. Condensed azo pigments such as CI Pigment Yellow 95 (Condensed Azo Yellow GR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Yellow 115 (such as quinoline yellow lake); I. Basic dye lake pigments such as CI Pigment Yellow 18 (Thioflavin Lake, etc.), anthraquinone pigments such as Flavantron Yellow (Y-24), isoindolinone pigments such as Isoindolinone Yellow 3RLT (Y-110), and quinophthalone yellow Quinophthalone pigments such as (Y-138), isoindoline pigments such as isoindoline yellow (Y-139), C.I. I. Nitroso pigments such as C.I. Pigment Yellow 153 (nickel nitroso yellow, etc.); I. And metal complex salt azomethine pigments such as CI Pigment Yellow 117 (copper azomethine yellow, etc.).

  C. As a thing which exhibits red or magenta color, C.I. I. Monoazo pigments such as CI Pigment Red 3 (Toluidine Red, etc.); I. Disazo pigments such as C.I. Pigment Red 38 (Pyrazolone Red B, etc.); I. Pigment Red 53: 1 (Lake Red C, etc.) and C.I. I. Azo lake pigments such as C.I. Pigment Red 57: 1 (Brilliant Carmine 6B); I. Condensed azo pigments such as C.I. Pigment Red 144 (condensed azo red BR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Red 174 (Phloxine B Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Red 81 (Rhodamine 6G 'lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Red 177 (eg, dianthraquinonyl red); I. Thioindigo pigments such as C.I. Pigment Red 88 (Thioindigo Bordeaux, etc.); I. Perinone pigments such as C.I. Pigment Red 194 (perinone red, etc.); I. Perylene pigments such as C.I. Pigment Red 149 (perylene scarlet, etc.); I. Pigment violet 19 (unsubstituted quinacridone), C.I. I. Quinacridone pigments such as CI Pigment Red 122 (quinacridone magenta, etc.); I. Isoindolinone pigments such as CI Pigment Red 180 (isoindolinone red 2BLT, etc.); I. And alizarin lake pigments such as CI Pigment Red 83 (Mada Lake, etc.).

  As a pigment exhibiting blue or cyan, C.I. I. Disazo pigments such as C.I. Pigment Blue 25 (Dianisidine Blue, etc.); I. Phthalocyanine pigments such as C.I. Pigment Blue 15 (phthalocyanine blue, etc.); I. Acidic dye lake pigments such as C.I. Pigment Blue 24 (Peacock Blue Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Blue 1 (Viclotia Pure Blue BO Lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Blue 60 (Indantron Blue, etc.); I. And alkali blue pigments such as CI Pigment Blue 18 (Alkali Blue V-5: 1).

As a pigment exhibiting green, C.I. I. Pigment green 7 (phthalocyanine green), C.I. I. Phthalocyanine pigments such as C.I. Pigment Green 36 (phthalocyanine green); I. And azo metal complex pigments such as CI Pigment Green 8 (Nitroso Green).
As a pigment exhibiting an orange color, C.I. I. An isoindoline pigment such as C.I. Pigment Orange 66 (isoindoline orange); I. And anthraquinone pigments such as CI Pigment Orange 51 (dichloropyrantron orange).

Examples of the black pigment include carbon black, titanium black, and aniline black.
Specific examples of the white pigment include basic lead carbonate (2PbCO ₃ Pb (OH) ₂ , so-called silver white), zinc oxide (ZnO, so-called zinc white), titanium oxide (TiO ₂ , so-called titanium white), Strontium titanate (SrTiO ₃ , so-called titanium strontium white) or the like can be used.

  Here, titanium oxide has a smaller specific gravity than other white pigments, a large refractive index, and is chemically and physically stable, so that it has a large hiding power and coloring power as a pigment. Excellent durability against other environments. Therefore, it is preferable to use titanium oxide as the white pigment. Of course, other white pigments (may be other than the listed white pigments) may be used as necessary.

For dispersion of the pigment, for example, a dispersion device such as a ball mill, a sand mill, an attritor, a roll mill, a jet mill, a homogenizer, a paint shaker, a kneader, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, or a wet jet mill is used. Can do.
It is also possible to add a dispersant when dispersing the pigment. Examples of the dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long-chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a high molecular weight unsaturated acid ester, a high molecular weight copolymer, a modified polyacrylate, an aliphatic polyacrylate. Carboxylic acid, naphthalenesulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester, pigment derivative and the like. It is also preferable to use a commercially available polymer dispersant such as Solsperse series manufactured by Nihon Librisol.
Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids can be used within a range not impeding the effects of the present invention, and it is preferable to add 1 to 50 parts by mass with respect to 100 parts by mass of the pigment.

  In the ink composition, as a dispersion medium for various components such as pigments, a solvent may be added, and the cationic polymerizable compound that is a low molecular weight component without a solvent may be used as a dispersion medium. The ink composition of the invention is a radiation curable ink, and is preferably solvent-free in order to be cured after the ink is applied to a recording medium. This is because if the solvent remains in the cured ink image, the solvent resistance deteriorates and the remaining solvent VOC (Volatile Organic Compound) affects. From such a viewpoint, it is preferable to use a polymerizable compound as the dispersion medium, and in particular, to select a radically polymerizable monomer having the lowest viscosity from the viewpoint of improving dispersibility and handling properties of the ink composition.

  The average particle diameter of the pigment is preferably 0.02 to 0.5 μm, and more preferably 0.08 to 0.5 μm. The selection of pigment, dispersant, dispersion medium, dispersion conditions, and filtration conditions are set so that the maximum particle size is 5 μm or less (preferably 3 μm or less). By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.

[dye]
Next, the dyes preferably used as the colorant in the present invention will be described.
The dye can be appropriately selected from conventional compounds (dyes). Specific examples include dyes described in paragraphs [0023] to [0089] of JP-A No. 2002-114930.
Examples of yellow dyes include, for example, phenols, naphthols, anilines, pyrazolones, pyridones, aryl or heteryl azo dyes having open-chain active methylene compounds as coupling components, for example, open-chain active methylene compounds as coupling components Azomethine dyes having, for example, methine dyes such as benzylidene dyes and monomethine oxonol dyes, for example, quinone dyes such as naphthoquinone dyes and anthraquinone dyes, and other dyes include quinophthalone dyes, nitro, Nitroso dyes, acridine dyes, acridinone dyes and the like can be mentioned.
Examples of the magenta dye include phenols, naphthols, anilines, pyrazolones, pyridones, pyrazolotriazoles, and ring-closing active methylene compounds (for example, dimedone, barbituric acid, 4-hydroxycoumarin) as coupling components. Derivatives), electron-rich heterocycles (eg, pyrrole, imidazole, thiophene, thiazole derivatives), or aryl or heteryl azo dyes, eg, azomethine dyes having pyrazolones, pyrazolotriazoles as coupling components, eg, arylidene dyes, styryl Dyes, merocyanine dyes, methine dyes such as oxonol dyes, carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes, such as naphthoquinone, anthraquinone, anthrone Quinone dyes such Rapiridon, can be mentioned condensed polycyclic dyes such as, for example, dioxazine dye.
Examples of cyan dyes include azomethine dyes such as indoaniline dyes and indophenol dyes, cyanine dyes, oxonol dyes, polymethine dyes such as merocyanine dyes, diphenylmethane dyes, triphenylmethane dyes, carbonium dyes such as xanthene dyes, Examples of phthalocyanine dyes and anthraquinone dyes include phenols, naphthols, anilines, pyrrolopyrimidin-one, aryl or heteryl azo dyes having pyrrolotriazin-one derivatives, and indigo / thioindigo dyes as coupling components.

Each of the dyes may exhibit yellow, magenta, and cyan colors only after a part of the chromophore is dissociated. In this case, the counter cation is an inorganic cation such as an alkali metal or ammonium. Alternatively, it may be an organic cation such as pyridinium, quaternary ammonium salt, or a cationic polymer having a partial structure thereof.
The dye used in the present invention is preferably oil-soluble. Specifically, it means that the solubility in water at 25 ° C. (the mass of the dye dissolved in 100 g of water) is 1 g or less, preferably 0.5 g or less, more preferably 0.1 g or less. Therefore, a so-called water-insoluble oil-soluble dye is preferably used.
The dye used in the present invention preferably has an oil-solubilizing group introduced into the above-described dye mother core in order to dissolve the necessary amount in the ink composition.
As the oil-solubilizing group, long chain, branched alkyl group, long chain, branched alkoxy group, long chain, branched alkylthio group, long chain, branched alkylsulfonyl group, long chain, branched acyloxy group, long chain, branched alkoxycarbonyl group, Long chain, branched acyl group, long chain, branched acylamino group long chain, branched alkylsulfonylamino group, long chain, branched alkylaminosulfonyl group and these long chains, aryl groups containing branched substituents, aryloxy groups, aryloxycarbonyl Group, arylcarbonyloxy group, arylaminocarbonyl group, arylaminosulfonyl group, arylsulfonylamino group and the like.
In addition, for water-soluble dyes having carboxylic acid and sulfonic acid, long chain, branched alcohol, amine, phenol, aniline derivatives are used as oil-solubilizing alkoxycarbonyl groups, aryloxycarbonyl groups, alkylaminosulfonyl groups, A dye may be obtained by conversion to an arylaminosulfonyl group.
The oil-soluble dye preferably has a melting point of 200 ° C. or lower, more preferably has a melting point of 150 ° C. or lower, and still more preferably has a melting point of 100 ° C. or lower. By using an oil-soluble dye having a low melting point, the precipitation of dye crystals in the ink composition is suppressed, and the storage stability of the ink composition is improved.
Further, it is desirable that the oxidation potential is noble (high) in order to improve fading, particularly resistance to oxidizing substances such as ozone and curing characteristics. For this reason, as the oil-soluble dye used in the present invention, those having an oxidation potential of at least 1.0 V (vs SCE) are preferably used [according to the description in the claims]. The oxidation potential is preferably higher, the oxidation potential is more preferably 1.1 V (vs SCE) to 2.0 V, and particularly preferably 1.15 V (vs SCE) to 2.0 V.

As the yellow dye, a compound having a structure represented by the general formula (Y-I) described in JP-A No. 2004-250483 is preferable.
Particularly preferred dyes are dyes represented by the general formulas (Y-II) to (Y-IV) described in paragraph [0034] of JP-A No. 2004-250483. And the compounds described in paragraph numbers [0060] to [0071] of JP-A-250483. The oil-soluble dye of the general formula (Y-I) described in the publication may be used not only for yellow but also for any color ink such as black ink and red ink.
The magenta dye is preferably a compound having a structure represented by the general formulas (3) and (4) described in JP-A No. 2002-114930. Specific examples include paragraphs of JP-A No. 2002-114930. Examples include the compounds described in [0054] to [0073].
Particularly preferred dyes are azo dyes represented by the general formulas (M-1) to (M-2) described in paragraph numbers [0084] to [0122] of JP-A No. 2002-121414, and specific examples Examples thereof include compounds described in paragraph numbers [0123] to [0132] of JP-A No. 2002-121414. The oil-soluble dyes represented by the general formulas (3), (4) and (M-1) to (M-2) described in the publication are used not only for magenta but also for any color ink such as black ink and red ink. May be.
Examples of the cyan dye include dyes represented by formulas (I) to (IV) described in JP-A No. 2001-181547, and paragraphs [0063] to [0078] of JP-A No. 2002-121414. The dyes represented by the general formulas (IV-1) to (IV-4) described above are preferred, and specific examples include paragraph numbers [0052] to [0066] of JP-A No. 2001-181547. Examples thereof include the compounds described in paragraph Nos. [0079] to [0081] of Kai 2002-121414.
Particularly preferred dyes are phthalocyanine dyes represented by general formulas (CI) and (C-II) described in paragraphs [0133] to [0196] of JP-A No. 2002-121414, A phthalocyanine dye represented by formula (C-II) is preferred. Specific examples thereof include the compounds described in JP-A No. 2002-121414, paragraph numbers [0198] to [0201]. The oil-soluble dyes of the formulas (I) to (IV), (IV-1) to (IV-4), (CI) and (C-II) are not only cyan but also black ink or green ink. It may be used for inks of any color.

[Oxidation potential]
The oxidation potential value (Eox) of the dye in the present invention can be easily measured by those skilled in the art. Regarding this method, for example, “New Instrumental Methods in Electrochemistry” by P. Delahay (1954, published by Interscience Publishers), AJBard et al. “Electrochemical Methods” (1980, published by John Wiley & Sons), Akira Fujishima et al. It is described in the book "Electrochemical measurement method" (1984, published by Gihodo Publishing Co., Ltd.).

Specifically, the oxidation potential is measured by placing a test sample in a solvent such as dimethylformamide or acetonitrile containing a supporting electrolyte such as sodium perchlorate or tetrapropylammonium perchlorate in the range of 1 × 10 ⁻² to 1 × 10 ⁻⁶ mol / It is measured as a value relative to SCE (saturated calomel electrode) using various voltammetry (polarography using a dropping mercury electrode, cyclic voltammetry, a method using a rotating disk electrode, etc.). Although this value may be deviated by several tens of mil volts due to the influence of the liquid potential difference or the liquid resistance of the sample solution, the reproducibility of the potential can be ensured by inserting a standard sample (for example, hydroquinone).
In the present invention, SCE (saturated calomel) is used as a reference electrode in N, N-dimethylformamide (concentration of dye is 0.001 mol / liter) containing 0.1 mol / liter of tetrapropylammonium perchlorate as a supporting electrolyte. Electrode), a value measured using a graphite electrode as a working electrode and a platinum electrode as a counter electrode (vsSCE) was defined as the oxidation potential of the dye.
The value of Eox represents the ease of electron transfer from the sample to the electrode, and the greater the value (the higher the oxidation potential), the more difficult the electron transfer from the sample to the electrode, in other words, the less easily oxidized. In relation to the structure of the compound, the oxidation potential becomes more noble by introducing an electron withdrawing group, and the oxidation potential becomes lower by introducing an electron donating group. In the present invention, in order to lower the reactivity with ozone as an electrophile, it is desirable to introduce an electron withdrawing group into the dye skeleton to make the oxidation potential more noble.
Specific examples of preferable dyes used in the present invention are shown below, but the dyes used in the present invention are not limited to the following specific examples. In the chemical formula, Me represents a methyl group, and Et represents an ethyl group.

[Other ingredients]
Hereinafter, various additives that can be contained in the ink composition of the present invention as needed are described.
[Ultraviolet absorber]
From the viewpoint of improving the weather resistance of the resulting image and preventing discoloration, an ultraviolet absorber can be used.
Examples of the ultraviolet absorber are described in JP-A-58-185679, JP-A-61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. Benzotriazole compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194433, US Pat. No. 3,214,463, etc. Cinnamic acid compounds described in JP-A-10-88106, JP-A-4-298503, JP-A-8-53427, JP-A-8-239368, JP-A-10-182621, JP The triazine compounds described in JP-A-8-501291, Research Disclosure No. Examples thereof include compounds described in No. 24239, compounds that emit ultraviolet light by absorbing ultraviolet rays typified by stilbene and benzoxazole compounds, so-called fluorescent brighteners, and the like.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass with respect to the total mass of the ink composition as long as the effects of the present invention are not hindered.

〔Antioxidant〕
An antioxidant can be added to improve the stability of the ink composition. Examples of the antioxidant include European published patents, 223739, 309401, 309402, 310551, 310552, 359416, and 3435443. JP, 54-85535, 62-262417, 63-113536, 63-163351, JP-A-2-262654, JP-A-2-71262, Examples thereof include those described in Kaihei 3-121449, JP-A-5-61166, JP-A-5-119449, US Pat. No. 4,814,262, US Pat. No. 4,980,275, and the like.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass with respect to the total mass of the ink composition as long as the effects of the present invention are not hindered.

[Anti-fading agent]
In the ink composition of the present invention, various organic and metal complex anti-fading agents can be used. Examples of the organic anti-fading agent include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles. Examples of the metal complex anti-fading agent include nickel complexes and zinc complexes. No. 17643, No. VII, I to J, ibid. 15162, ibid. No. 18716, page 650, left column, ibid. No. 36544, page 527, ibid. No. 307105, page 872, ibid. The compounds described in the patent cited in No. 15162 and the compounds included in the general formulas and compound examples of representative compounds described in JP-A-62-215272, pages 127 to 137 can be used. .
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 5% by mass with respect to the total mass of the ink composition as long as the effects of the present invention are not hindered.

[Conductive salts]
Conductive salts such as potassium thiocyanate, lithium nitrate, ammonium thiocyanate, and dimethylamine hydrochloride can be added to the ink composition of the present invention for the purpose of controlling ejection properties.
The amount to be added is appropriately selected according to the purpose, but is generally about 0.001 to 1.0% by mass with respect to the total mass of the ink composition as long as the effects of the present invention are not hindered. .

〔solvent〕
In order to improve the adhesion to the recording medium, it is also effective to add a very small amount of an organic solvent to the ink composition of the present invention.
Examples of the solvent include ketone solvents such as acetone, methyl ethyl ketone, and diethyl ketone, alcohol solvents such as methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, and tert-butanol, and chlorine such as chloroform and methylene chloride. Solvents, aromatic solvents such as benzene and toluene, ester solvents such as ethyl acetate, butyl acetate and isopropyl acetate, ether solvents such as diethyl ether, tetrahydrofuran and dioxane, glycols such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether And ether solvents.
In this case, it is effective to add in a range that does not cause a problem of solvent resistance and VOC, and the amount of the solvent is 0.1 to the total mass of the ink composition as long as the effect of the present invention is not hindered. 5 mass% is preferable and 0.1-3 mass% is more preferable.

[Polymer compound]
Various polymer compounds can be added to the ink composition in order to adjust film properties. Examples of the polymer compound include styrene polymers, acrylic polymers, cyclic ether polymers, polyvinyl butyral resins, polyurethane resins, polyamide resins, polyester resins, epoxy resins, phenol resins, polycarbonate resins, polyvinyl butyral resins, and polyvinyl formal resins. Shellac, vinyl resin, acrylic resin, rubber resin, wax, and other natural resins can be used. Two or more of these may be used in combination. Of these, copolymerization of styrene monomers, acrylic monomers, and cyclic ethers is preferred. Furthermore, as a copolymer composition of the polymer binder, a copolymer containing “cyclic ether group-containing monomer” and “vinyl ether group-containing monomer” as a structural unit is also preferably used.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10.0% by mass with respect to the total mass of the ink composition as long as the effects of the present invention are not hindered. .

[Surfactant]
Examples of the surfactant include those described in JP-A Nos. 62-173463 and 62-183457. For example, anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene blocks Nonionic surfactants such as copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. An organic fluoro compound may be used in place of the surfactant. The organic fluoro compound is preferably hydrophobic. Examples of the organic fluoro compounds include fluorine surfactants, oily fluorine compounds (eg, fluorine oil) and solid fluorine compound resins (eg, tetrafluoroethylene resin). No. (columns 8 to 17) and those described in JP-A Nos. 62-135826.
The addition amount is appropriately selected according to the purpose, but is generally within the range of 0.001 to 5.0% by mass with respect to the total mass of the ink composition as long as the effects of the present invention are not hindered. .

In addition to this, if necessary, for example, leveling additives, matting agents, waxes for adjusting film physical properties, polymerization to inhibit the adhesion to recording media such as polyolefin and PET, and the like, The tackifier which does not do can be contained.
As the tackifier, specifically, a high-molecular-weight adhesive polymer described in JP-A-2001-49200, 5-6p (for example, (meth) acrylic acid and an alkyl group having 1 to 20 carbon atoms). An ester of an alcohol having an alcohol, an ester of (meth) acrylic acid and an alicyclic alcohol having 3 to 14 carbon atoms, and an ester of (meth) acrylic acid and an aromatic alcohol having 6 to 14 carbon atoms. Polymer) and low molecular weight tackifying resins having a polymerizable unsaturated bond.

The ink composition of the present invention preferably has an ink viscosity of 30 mPa · s or less, more preferably 5 to 20 mPa · s at the temperature at the time of ejection in consideration of ejection properties, so that it falls within the above range. It is preferable to adjust the composition ratio as appropriate. The temperature at the time of injection is generally 25 to 90 ° C, preferably 25 to 80 ° C, and particularly preferably 40 to 80 ° C. The ink viscosity at 25 to 30 ° C. is preferably 200 mPa · s or less, more preferably 7 to 100 mPa · s. By setting the viscosity at room temperature high, even when a porous recording medium is used, ink penetration into the recording medium can be prevented, uncured monomer can be reduced, and odor can be reduced. Dot bleeding at the time of landing can be suppressed, and as a result, the image quality is improved. When the ink viscosity at 25 to 30 ° C. is larger than 200 mPa · s, there may be a problem in the delivery of the ink liquid.
The surface tension of the ink composition of the present invention is preferably 20 to 30 mN / m, more preferably 23 to 28 mN / m. When recording on various recording media such as polyolefin, PET, coated paper, and non-coated paper, 20 mN / m or more is preferable from the viewpoint of bleeding and penetration, and the wettability is preferably 30 mN / m or less.

The ink composition of the present invention thus adjusted is an inkjet recording ink. The ink composition is printed on a recording medium by an inkjet printer, and then the printed ink composition is irradiated with an active energy ray and cured to perform recording.
In the printed matter obtained with this ink, the image portion is cured by irradiation with active energy rays such as ultraviolet rays, and the strength of the image portion is excellent. Therefore, in addition to image formation with ink, for example, an ink receiving layer of a lithographic printing plate It can be used for various purposes such as formation of (image part).

The ink composition of the present invention is an ink for ink jet recording. There are no particular restrictions on the ink jet recording method, for example, a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses the vibration pressure of a piezo element, and an electrical signal that is acoustic Either an acoustic ink jet system that irradiates ink by irradiating it with ink instead of using a beam, or a thermal ink jet system that uses ink to form bubbles by heating the ink and use the generated pressure. Also good. The inkjet recording method includes a method of ejecting a large number of low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent. A method using ink.
Among these, the ink is suitable as a drop-on-demand type (pressure pulse type) ink jet recording ink using a piezo element.

<Image forming method and recorded matter thereof>
The image forming method of the present invention includes an image recording step of recording an image on a recording medium using the ink composition of the present invention described above, and curing by irradiating the recorded image with active energy rays (active rays). And an image curing step to be provided. In the present invention, a polymerizable compound that contributes to imaging by using active energy rays in the image curing step, recording an image on a recording medium in the image recording step, and then irradiating the recorded image with active energy rays. As the polymerization and curing proceed, the image is cured well and an image having high fastness can be formed.
The recorded matter obtained with this ink has an image portion cured by irradiation with active energy rays such as ultraviolet rays and is excellent in strength of the image portion. For example, it is used as an ink receiving layer (image portion) of a lithographic printing plate. You can also.

In the image recording step, we apply an inkjet recording method using an inkjet printer. Specifically, an aspect in which the image is inkjet-recorded by discharging an ink composition in the image recording step is preferable. In the ink jet recording method, image recording is performed on a recording medium using the ink composition of the present invention, and there are no particular restrictions on the ink discharge nozzles (for example, for an ink jet printer) used at that time, and the purpose and application It can be appropriately selected according to the like. There is no restriction | limiting in particular in an inkjet recording system, and it is as above-mentioned specifically.

  In the image curing step, an exposure process for accelerating polymerization and curing can be performed using a light source that emits active energy rays in a wavelength region corresponding to the sensitive wavelength of the ink composition. Specifically, a light source that emits active rays belonging to a wavelength region of 240 to 450 nm, for example, LD, LED, fluorescent lamp, low-pressure mercury lamp, high-pressure mercury lamp, metal halide lamp, carbon arc lamp, xenon lamp, chemical lamp, etc. It can be suitably performed. Preferred light sources include LEDs, high pressure mercury lamps, and metal halide lamps. What is necessary is just to select an exposure time and light quantity suitably according to the grade of the polymerization hardening of the polymeric compound which concerns on this invention.

[Inkjet recording method and inkjet recording apparatus]
Next, an ink jet recording method and an ink jet recording apparatus that can be suitably employed in the ink composition of the present invention will be described below.
In the ink jet recording method, it is preferable that the ink composition is heated to 40 to 80 ° C. to lower the viscosity of the ink composition to 30 mPa · s or less, and then ejected. By using this method, high ejection stability is achieved. Can be realized. In general, radiation curable ink compositions generally have a higher viscosity than aqueous inks, so that the viscosity fluctuation range due to temperature fluctuations during printing is large. This viscosity variation of the ink composition directly affects the droplet size and droplet ejection speed as it is, which causes image quality deterioration. Therefore, it is necessary to keep the ink composition temperature as constant as possible during printing. is there. The control range of the ink composition temperature is preferably set temperature ± 5 ° C., more preferably set temperature ± 2 ° C., and particularly preferably set temperature ± 1 ° C.

One feature of the ink jet recording apparatus is that it includes a means for stabilizing the temperature of the ink composition, and the portion to be kept at a constant temperature is a piping system from an ink tank (an intermediate tank if there is an intermediate tank) to the nozzle ejection surface. All of the members are targeted.
The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors in each piping portion and perform heating control according to the ink composition flow rate and the environmental temperature. Moreover, it is preferable that the head unit to be heated is thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time required for heating or to reduce the loss of thermal energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

The ink composition of the present invention can be a preferable active energy ray-curable ink composition by containing a photopolymerization initiator.
The irradiation conditions of active energy rays in such an ink will be described. A basic irradiation method is disclosed in JP-A-60-132767. Specifically, a light source is provided on both sides of the head unit, and the head and the light source are scanned by a shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In WO99 / 54415, as an irradiation method, a method using an optical fiber or a method in which a collimated light source is applied to a mirror surface provided on the side surface of the head unit to irradiate the recording unit with UV light is disclosed. These irradiation methods can be used in the ink composition of the present invention.

  In the ink composition of the present invention, the ink composition is heated to a constant temperature, and the time from landing to irradiation is desirably 0.01 to 0.5 seconds, preferably 0.01 to 0.00. It is to irradiate active energy rays after 3 seconds, more preferably from 0.01 to 0.15 seconds. Thus, by controlling the time from landing to irradiation to an extremely short time, it is possible to prevent the landing ink from bleeding before curing. Also, since the ink composition can be exposed to a porous recording medium before it penetrates deeper than the light source reaches, unreacted monomer remains, and as a result, odor can be reduced. Can do. By using the inkjet recording method described above and the ink composition of the present invention in combination, a great synergistic effect is brought about. In particular, when an ink composition having an ink viscosity of 200 mPa · s or less at 25 ° C. is used, a great effect can be obtained. By adopting such a recording method, the dot diameter of the landed ink can be kept constant even on various recording media having different surface wettability, and the image quality is improved. In addition, in order to obtain a color image, it is preferable to superimpose in order from the color with the lowest brightness. When inks with low lightness are stacked, it is difficult for the irradiation rays to reach the lower ink, and inhibition of curing sensitivity, increase of residual monomers, generation of odor, and deterioration of adhesion tend to occur. Irradiation can be performed by injecting all colors and exposing them together, but exposure for each color is preferable from the viewpoint of curing acceleration.

  There is no restriction | limiting in particular as an inkjet recording device which discharges the ink composition of this invention, A commercially available inkjet recording device can be used. That is, the ink composition of the present invention can be recorded on a recording medium using a commercially available inkjet recording apparatus.

[Recording medium]
The recording medium used in the present invention is not particularly limited, and examples thereof include an ink-permeable recording material and an ink-impermeable recording material, any of which can be used.

  Examples of the ink-permeable recording material include plain paper, inkjet exclusive paper, coated paper, electrophotographic co-paper, cloth, non-woven fabric, porous film, and polymer absorber. These are described as “recording materials” in Japanese Patent Application Laid-Open No. 2001-181549.

  From the viewpoint of effectively expressing the effects of the present invention, it is preferable to use a non-ink-permeable (non-absorbing) recording material. Examples of the ink-impermeable recording material include art paper, synthetic resin, rubber, resin-coated paper, glass, metal, earthenware, and wood. In addition, in terms of adding each function, a base material obtained by combining a plurality of these materials can also be used.

As the synthetic resin, any synthetic resin can be used. For example, polyester resin (polyethylene terephthalate, polybutadiene terephthalate, etc.), polyolefin resin (polyvinyl chloride, polystyrene, polyethylene, polyurethane, polypropylene, etc.), acrylic resin, Examples include polycarbonate, acrylonitrile-butadiene-styrene copolymer, diacetate, triacetate, polyimide, cellophane, celluloid, and polyvinyl alcohol.
There is no restriction | limiting in particular about the shape of the base material using a synthetic resin, and its thickness, Any of a film form, a card | curd shape, or a block shape may be sufficient, and it can select suitably according to the desired objective. The synthetic resin may be either transparent or opaque.

  As the usage form of the synthetic resin, it is one of the preferred forms used in the form of a film used for so-called soft packaging, and various non-absorbable plastics and films thereof can be used. Various plastics films include, for example, PET (polyethylene terephthalate) film, OPS (stretched polystyrene) film, OPP (stretched polypropylene) film, ONy (biaxially stretched nylon) film, PVC (polyvinyl chloride) film, PE (Polyethylene) film, TAC (triacetylcellulose) film, etc. can be mentioned.

  Examples of the resin-coated paper include a paper support in which one side or both sides of the paper is coated with a polyolefin resin and the like, and a paper support in which both sides of the paper are laminated with a polyolefin resin is particularly preferable.

  As described above, an image can be formed by image recording using the ink composition of the present invention, and a suitable recorded product can be obtained. In this recorded matter, since the ink used for image formation contains fine pigment particles uniformly and stably dispersed, it has a high-quality image with excellent color development and sharpness, and the weather resistance of the image Therefore, it can be applied to a wide range of fields.

The ink composition of the present invention includes a basic surfactant. As a result, particularly in a cationically polymerizable ink, an undesirable polymerization reaction during storage with time can be suppressed, and excellent storage stability and ejection stability are exhibited. Further, the decrease in curability that occurs when a general low molecular weight polymerization inhibitor is added and the accompanying decrease in adhesion to the recording medium are suppressed. As a result, it is possible to form a high-quality image excellent in all of color developability, dischargeability, curability, film strength, and adhesion to a recording medium.
Furthermore, the printed matter of the present invention can be obtained by printing the ink composition of the present invention on a recording medium with an ink jet printer, and then preferably irradiating the cured ink composition with an active energy ray and curing. it can. The printed matter of the present invention has a high-quality image excellent in color developability and sharpness, and is excellent in the weather resistance of the image, and therefore can be applied to a wide range of fields.
In addition, the ink composition of the present invention can be used for normal printing to form a sharp image with excellent color developability and not only to obtain a high-quality printed matter, but also for the production of resists, color filters, optical discs and the like. Can also be suitably used, and is also useful as an optical modeling material.
Furthermore, the ink composition of the present invention can form a high-quality image directly on a non-absorbable recording medium based on digital data by applying an ink jet recording method. For this reason, the ink composition of this invention can be used conveniently also for preparation of printed matter of a large area.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. Moreover,% in an Example is a mass reference | standard unless there is particular notice.
[Examples and Comparative Examples]
A polymerizable compound, a polymerization initiator, and a colorant were stirred and mixed at room temperature under atmospheric pressure with parts by mass shown in Table 1 to obtain dye ink or pigment ink samples 1 to 9.
The compounds in the table are as follows.
M-1 Tridecyl acrylate Nippon Kayaku Co., Ltd. M-2 NK ester AM-90G Shin-Nakamura Chemical Co., Ltd. M-3 NK ester A-400 Shin-Nakamura Chemical Co., Ltd. M- 4 NK Ester APG-700 M-5 NK Ester A-200 made by Shin-Nakamura Chemical Co., Ltd. M-6 1,6-hexanediol diacrylate made by Shin-Nakamura Chemical Co., Ltd. Daicel UCB Co., Ltd. * 1: Photoradical polymerization initiator, acylphosphine oxide (TOP-L, manufactured by BASF Japan)
* 2: The following compound MM-1 oxidation potential 1.39V (measured with ALS Model 610A manufactured by CH Instruments)

＊３：以下のようにして調製した顔料分散物Ｐ−１。
黒顔料（C.I.ピグメントブラック７、分子量）１０ｇ、高分子分散剤（日本リーブリゾール社製 Ｓｏｌｓｐｒｓｅ ３２０００）５ｇと重合性化合物（各インク組成物の重合性化合物種を表１に示すのと同じ割合で混合したもの）８５ｇを混合し、顔料粒子の粒径が０．０５〜０．３μｍの範囲となるように、通常の分散装置を用いて分散させ、次いで、加熱フィルターろ過を行って得た。

* 3: Pigment dispersion P-1 prepared as follows.
Black pigment (CI pigment black 7, molecular weight) 10 g, polymer dispersant (Solsprse 32000 manufactured by Nihon Librisol Co., Ltd.) 5 g and polymerizable compound (polymerizable compound species of each ink composition in the same proportion as shown in Table 1. 85 g of the mixture) was mixed and dispersed using an ordinary dispersing device so that the particle size of the pigment particles was in the range of 0.05 to 0.3 μm, and then filtered by heating filter.

[Test of printed sample]
The obtained ink composition was printed on a vinyl chloride film with an inkjet printer (printing density 300 dpi, droplet ejection frequency 4 kHz, nozzle number 64), and then with a Deep UV lamp (US-7, SP-7) at 15 mJ / cm. It exposed on the conditions used as energy of ² , and obtained the printing sample. The following test was performed on a print sample that had passed 10 minutes after printing.

(Discharge stability)
When ink was printed by an ink jet printer, A could be ejected without any problem, and C could cause non-ejection. (A is a problem-free level, B is a level that can be a problem in practice, and C is a level that is a problem in practice)
(Curable)
A tack-free test was performed on the printed surface. When the cured film was touched with a finger, A was given when there was no stickiness, B was given when there was a slight stickiness, and C was given when it was extremely sticky.
(Adhesion)
After cutting the cut surface in a grid pattern with a cutter, an adhesive tape was attached to the surface of the cured film, and then the remaining state of the cured film on the substrate when the adhesive tape was peeled was visually observed. The case where peeling was not observed was indicated as A, the case where partial peeling was observed as B, the case where remarkable peeling was observed as C, and the case where curing was insufficient and could not be measured as D.
(curl)
A 10 cm square vinyl chloride film (thickness 50 μm) was printed with a solid pattern of 8 cm square and 10 μm thickness, and the curl of the sample was measured after drying for 2 hours at room temperature. When the sample was placed on a horizontal base, the sum of the heights from the horizontal surfaces at the four corners was less than 2 cm, A was less than 10 cm, and B was 10 cm or more. In addition, the thing with insufficient hardening was set to D.
(odor)
After printing and drying for 1 hour, the odor of the cured film was removed, and A with little odor, B with odor, and C with significant odor.
(Light resistance)
The film on which the image was formed was irradiated with xenon light (100,000 lx) for 3 days using a weather meter (Atlas C.165), and the image density before and after the xenon irradiation was measured using a reflection densitometer (X-Rite 310TR). Measurements were made to determine the dye residual ratio. The reflection density was fixed at 1.0. The case where the dye residual ratio was 80% or more was designated as A, less than 80% as B, and less than 70% as C.

As shown in Table 1, in Samples 1 to 7, printed matter with less odor was obtained by using a large amount of monomer having a large molecular weight. In Samples 1 to 7, a printed matter having a small curl and excellent adhesion was obtained by using many samples having a molecular weight divided by the number of polymerizable functional groups of 250 or more. The light resistance and ink ejection stability were good for all inks. Among them, Samples 1 to 3 and 5 to 7 did not contain a monomer having a small value obtained by dividing the molecular weight by the number of polymerizable functional groups or a monomer having a small molecular weight, and more excellent printed materials with respect to odor and curability were obtained.
On the other hand, Samples 8 and 9 contain many monomers whose molecular weight divided by the number of polymerizable functional groups is less than 250, or contain many monomers with low molecular weight, and the printed matter is inferior in adhesion and curl, and odor is generated. did. In particular, curl and odor were practically problematic levels.
As a result, the ink composition of the present invention is excellent in the stability of the ink. When an image is formed using the ink composition, a good image can be formed. It can be seen that it has excellent adhesion to the recording medium.

Claims (9)

An ink composition comprising a) a photopolymerization initiator and b) a polymerizable compound, wherein the content of the polymerizable compound in b) is in the range of 70 to 99.9% by mass relative to the total mass of the ink composition. And 50% by mass or more of the total mass of the polymerizable compound of b) having a molecular weight per polymerizable functional group of 250 or more and 2000 or less , tridecyl acrylate, methoxypolyethylene glycol monoacrylate, polyethylene glycol diacrylate, and polypropylene glycol Ri least one polymerizable compound der selected from the group consisting of diacrylates, its content of molecular weight organic compounds of less than 250, relative to the total weight of the composition, Ru less than 10% by mass An ink composition for ink jet printing characterized by the above.   From the group consisting of tridecyl acrylate, methoxypolyethylene glycol monoacrylate, polyethylene glycol diacrylate, and polypropylene glycol diacrylate, wherein 75% by mass or more of the total mass of the polymerizable compound b) has a molecular weight of 300 or more per polymerizable functional group. The ink composition for ink jet printing according to claim 1, wherein the ink composition is at least one polymerizable compound selected. Ink jet ink composition according to claim 1 or 2, characterized in that it comprises a colorant. 4. The ink composition for ink jet printing according to claim 3 , wherein the colorant is selected from the group consisting of a pigment and an oil-soluble dye. The ink composition for ink jet printing according to claim 4 , wherein the oxidation potential of the oil-soluble dye is at least 1.0 V (vs SCE). Image forming method, which comprises an image recording step of recording an image on a recording medium by an ink jet recording which ejects ink jet ink composition according to any one of claims 1-5. An image recording step of recording an image on a recording medium using the ink composition for inkjet printing according to any one of claims 1 to 5 ,
An image curing step of irradiating and curing an active energy ray on the image recorded on the recording medium in the image recording step;
An image forming method comprising: The image forming method according to claim 7 , wherein in the image recording step, the image is recorded by inkjet recording in which the ink composition for inkjet printing is discharged. A recorded matter recorded using the ink composition for ink jet printing according to any one of claims 1 to 5 .